I don't think Spieler Eins is right, but I do think he has a point. Wii U software, in my experience, has been largely competent and polished but lacking in genius in favor of 'playing things safe.'
Take 3D World: It is a fact that the 3D series exists to bring 3D Mario in line with NSMB because the latter sells better than 3D Mario games. Miyamoto is on record numerous times talking about how 3D gaming left people behind and how that needed to be addressed. It is, moreover, evident in the game design of the 3D series, if Land more so than World. So you go from Galaxy, which was a revolution in 3D platforming, to a game that had as its mission to reset 3D platforming and bring it more in line with the NSMB series. The world design, art design, level design, etc. was brought somewhere between Galaxy 2 and NSMB.
Artistically and gameplay wise, the NSMB are very safe and have a rather bland aesthetic, at least in the eyes of many. You here it all the time. They are NSMB as in, so to speak, MB 1&2 (Japan), not as in MB 1, 2, 3, & World. Bringing that sort of direction to 3D Mario is going to disappoint a lot of people. I include myself among them. The project presents itself as a devolutionary rather than revolutionary project and that is on purpose.
On the other hand, there is plenty of Galaxy 2, which already was a step towards 2D Mario rules, preserved in 3D world in game design. I also remember it much better than any NSMB, which I tend to forget as soon as I've played. The game was fun, polished, and a good Galaxy 2 successor that hid its ambitions behind a coat of paint designed to lure people from NSMB to 3D Mario. It was trying not to appear to be the next big 3D platformer while being the next big 3D platformer.
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This idea that 2D platformers were the big item is evident throughout the entire Wii U and late Wii library. There is an overabundance of such games on Wii U when a more diversified catalog could have turned more heads. TF may be one of the best 2D platformers ever, but the idea that Retro should also be making 2D platformers was a bad one. I don't get why we understand this point when we argue Nintendo should not go third party for the sake of the breadth of their catalog but fail to register this point when it comes to critiquing the Wii U library.
Yes, BotW looks like ambitious Nintendo again. Yes, Splatoon and Mario Maker look like ambitious Nintendo again. But all of these things are coming way too late.
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I think the Wii U library is good. It has the most compelling exclusives to me of any console this generation so far. At the same time, the catalog is incredibly narrow and it pales in terms of ambition and artistic imagination compared to previous Nintendo catalogs. I think both of these things can be true. Is the latter the reason why Wii U failed? Not alone, no. But it definitely is part of it.
NX needs a broader Nintendo first party and revolutionary projects. BotW is looking to be one. Miyamoto is hinting at the next Mario being one. We'll have to see how things pan out.